Re: [RFC PATCH] vreportf: ensure sensible ordering of normal and error output

>   - flushing causes us to block. This implies our stdout is connected to
>     a pipe or socket, and the other side is not expecting to read. A
>     plausible case here is a client sending us a big input which we find
>     to be bogus (maybe index-pack checking an incoming pack). We call
>     die() to complain about the input, but the client is still writing.
>     In the current code, we'd write out our error and then exit; the
>     client would get SIGPIPE or a write() error and abort. But with a
>     flush here, we could block writing back to the client, and now we're
>     in a deadlock; they are trying to write to us but we are no longer
>     reading, and we are blocked trying to get out a little bit of
>     irrelevant stdout data.
>
> Of the two, the deadlock case worries me more, just because it would be
> quiet subtle and racy. As I said, I think we may be OK, but my reasoning
> there is pretty hand-wavy.